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Clip-in filters for Canon 6d - Vignetting Issues - Mirror block

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#1 cfosterstars

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Posted 16 March 2017 - 11:28 PM

I tried out my newly modified Canon 6D with a 70-300mm Canon EF lens and it seem to work well. I was using a Astronomik Luminance "full frame" canon clip in filter. I had seen the APS-C size filters used with non-full frame canon cameras on various sites and youtube videos and they looked like a great fit for DSLR imaging. I ordered three of them - 1) Astronomk Luminance (UVIR blocking), 2) OPTOLONG CLS-CCD filter, and 3) and OPTOLONG OWB filter so I could use the modified camera with normal imaging. I was disappointed to realize after I purchased them, that when installed, they block the filp mirror in the up position and render the view finder useless. I basically chalked that up to my own lack of due diligence since I found that disclaimer on the Astronomik web site after the fact. 

 

However, this is not the main issue. I discovered the first time I was using the 6D on my Meade LX200ACF at prime focus, that I had vignetting. WHAT!!

 

I had worked very hard to figure out how to get as wide a field with the full frame camera as possible without vignetting. Every focal reducer that I could find would vignette badly. Prior to modification, I was only using a clear glass 2" filter on the end of a 48mm canon wide 2" camera adapter. That showed basically no vignetting. I posted several decent images with the unmodified camera. Then I sent it off to Gary Honis for modification. The clip-in luminance was to be my baseline filter and I first tested it with the Canon EF lens and it look OK for vignetting. I shot some wide field with that camera and lens and thought that this was working.

 

I had a bunch of bad weather and when I finally got some clear skies, I went out even though it was basically a mostly full moon. I started taking flats and saw to my horror, that the flats showed rectangular vignetting. Here is an example:

 

EON 6D TEST FLAT Tv11600s 1600iso LUMINANCE 20170316 21h00m56s210ms
 
 
I suspected the clip-in filter has some how gotten cocked in the camera. I pulled of the camera and check it out. It was fine as far as I could see, but I re-position the filter and tried again with exactly the same results. I thought that this cant be. It cant be the filter itself. Its "designed for full frame cameras". So I pulled out my old 2" UVIR blocking filter from my old nose piece and tried that out. Surely this cant be better. Well this was what I got:
 
EON 6D TEST FLAT Tv12000s 1600iso UVIR 20170316 20h33m59s354ms

 

I retried the seating of the clip-in filter three times with no effect what so ever. I then tried the other two filters and the OPTOLONGS are slightly worse but not much. This is the CLS-CCD clip-in:

 

EON 6D TEST FLAT Tv1800s 1600iso CLSCCD 20170316 21h04m17s079ms

 

After about 300$ wasted here, needless to say, I am disappointed. They seem to work with the Canon EF lenses and the vignetting is not as noticeable or at least I did not notice it.

 

My recommendation is to use 2" round filters for a modified full frame camera on 48mm-based T-ring sized adapters to avoid vignetting. 



#2 leveye  Happy Birthday!

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Posted 17 March 2017 - 12:15 AM

I've always had great results with the innovator of this type of clip in filter. Astronomiks. Maybe give them a try.

 

http://www.astronomik.com/en/



#3 nathang123

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Posted 17 March 2017 - 02:47 AM

I was using a Astronomik Luminance "full frame" canon clip in filter.

 

I've always had great results with the innovator of this type of clip in filter. Astronomiks. Maybe give them a try.

 

http://www.astronomik.com/en/

I think he's not very pleased with their product. Did you get a different result on a full frame camera?



#4 Gucky

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Posted 17 March 2017 - 03:01 AM

I also was disappointed when I discovered this.
I was told by Mr. Neumann that this is normal behaviour because of the "extremely narrow light shaft on Canon's full frame cameras". Although they tried to minimise the frame of the filter a small amount of vigentting is unavoidable and can be corrected with flats.

 

I just thought for myself this should be noted on the products website...


Edited by Gucky, 17 March 2017 - 04:36 AM.


#5 johnpane

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Posted 17 March 2017 - 05:49 AM

I had seen the APS-C size filters used with non-full frame canon cameras on various sites and youtube videos and they looked like a great fit for DSLR imaging. I ordered three of them

 

...

 

However, ... I discovered the first time I was using the 6D on my Meade LX200ACF at prime focus, that I had vignetting. WHAT!!

You seem to be saying you are using filters designed for APS-C sensors on a full-frame camera. It does not seem surprising at all that there would be vignetting.



#6 Gary Honis

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Posted 17 March 2017 - 08:50 AM

Hi Chris,

 

I get the same vignetting with my Astronomik XL filters when imaging with my Full Spectrum 6D.  The vignetting can be removed when calibrating with flats.

 

I also get a stronger vignetting at the bottom of the frame caused by the flip mirror's shadow when using no filters with my 12" RC. Above the black bar at the bottom of the frame, I also get a brighter bar that sometimes is very difficult to remove.  See the flat image below.

Attached Thumbnails

  • Flat.JPG


#7 thompeters65

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Posted 17 March 2017 - 10:44 AM

Great discussion guys!! All the info is very helpful when I make decisions as I get into astrophotography!!

#8 cfosterstars

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Posted 17 March 2017 - 02:28 PM

 

I had seen the APS-C size filters used with non-full frame canon cameras on various sites and youtube videos and they looked like a great fit for DSLR imaging. I ordered three of them

 

...

 

However, ... I discovered the first time I was using the 6D on my Meade LX200ACF at prime focus, that I had vignetting. WHAT!!

You seem to be saying you are using filters designed for APS-C sensors on a full-frame camera. It does not seem surprising at all that there would be vignetting.

 

I am sorry if this was not clear. I was using and testing a Astronomik's clip in filter designed for full frame camera and NOT the clip in fiters for APS-C camera. They wont even mount in the full frame camera. 

 

I also was disappointed when I discovered this.
I was told by Mr. Neumann that this is normal behaviour because of the "extremely narrow light shaft on Canon's full frame cameras". Although they tried to minimise the frame of the filter a small amount of vigentting is unavoidable and can be corrected with flats.

 

I just thought for myself this should be noted on the products website...

I full agree. I e-mailed Astroniomik's directly and basically recieved the same response. It clearly should be noted on their web site. I believe that they will work well with canon lenses and that is what the manufacture said also. They just can work without vignetting on telescopes. The vignetting is the same on both my Meade LX200ACF 10" SCT and my Orion EON 115mm APO. Both scopes have about the same issue.



#9 cfosterstars

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Posted 17 March 2017 - 02:29 PM

I also was disappointed when I discovered this.
I was told by Mr. Neumann that this is normal behaviour because of the "extremely narrow light shaft on Canon's full frame cameras". Although they tried to minimise the frame of the filter a small amount of vigentting is unavoidable and can be corrected with flats.

 

I just thought for myself this should be noted on the products website...

I also did not find that the vignetting is correctable with flats. The edge fall off is too large for flats to fix well.



#10 cfosterstars

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Posted 17 March 2017 - 02:44 PM

Hi Chris,

 

I get the same vignetting with my Astronomik XL filters when imaging with my Full Spectrum 6D.  The vignetting can be removed when calibrating with flats.

 

I also get a stronger vignetting at the bottom of the frame caused by the flip mirror's shadow when using no filters with my 12" RC. Above the black bar at the bottom of the frame, I also get a brighter bar that sometimes is very difficult to remove.  See the flat image below.

This is a single 300s sub-exposure of NGC 4565 after calibration with darks, flats and bias with the Astronomik's full frame luminance clip in filter. This show very similar bright bar at the bottom due to the filp mirror I think. You can get rid of most of the effect, but now all.

 

I had to throw a significant brightening curves adjustment to show it well. 
 

I was not successful to fully correct it.

 

I am going to swap to 2" filters going forward. Not quite as elegant, but it gives better results. I will use them for my WF with canon lenses, but I will likely try renting a good lens first and test it out.

Attached Thumbnails

  • ASG_ECC0-437Size8-908_NL_BINT_C_CVT_NGC 4565_LIGHT_300S_800ISO_LUMINANCE_20170314-04H24M29S747MS.jpg

Edited by cfosterstars, 17 March 2017 - 02:44 PM.


#11 nathang123

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Posted 17 March 2017 - 05:34 PM

I have to say, if stacked and processed images are similar to the results here, that either cropping or going with a larger external filter would be prudent. It is a bit ugly.



#12 calypsob

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Posted 17 March 2017 - 07:55 PM

40-50 flats and 125-300 bias wipes it right out in pixinsight for me

#13 cfosterstars

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Posted 17 March 2017 - 09:59 PM

This was 109 at 240s frames @ ISO1600. I used 60 flat frames, 60 dark frames and 100 bias frames. I did not do any stretching since it was clear that I did not correct the image with this calibration and stacking.

 

6D_NGC4565_SM.jpg



#14 garret

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Posted 18 March 2017 - 04:09 AM

Your vignetting is negligible, here is the vignetting I have to deal with from my imaging telescope (Canon 5 D mk2 plus a 18000 dollar telescope).

Nearly all vignetting is coming from the camera itself.

Attached Thumbnails

  • vignetting.jpg


#15 Gary Honis

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Posted 18 March 2017 - 07:01 AM

Hi Chris,

 

Look at your histogram for your flats.   I've found the best flat when using DeepSky Stacker for calibrating is when the histogram bump is in the same position as for the light frame.

 

Gary



#16 cfosterstars

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Posted 18 March 2017 - 07:40 AM

Hi Chris,

 

Look at your histogram for your flats.   I've found the best flat when using DeepSky Stacker for calibrating is when the histogram bump is in the same position as for the light frame.

 

Gary

Gary,

 

Thanks for the tip. I thought that you only want the flats histogram to be in the middle. I did not know about matching the peak. I will give it a try. This is the processed image. I did have to crop significantly due to the vignetting of the clip in. 

 

_6D_NGC4565_MED.jpg



#17 Gary Honis

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Posted 18 March 2017 - 09:56 AM

Hi Chris,

 

For my six-minute images with my Full Spectrum 6D at ISO 1600 using my 12 inch RC my histogram for the light frames have the histogram bump in the middle.  So I take my flats so that the histogram bump is in the middle.  Sorry for the misunderstanding.

 

You can see my astro images with the Full Spectrum 6D here:

 

http://GaryHonis.com...6D Gallery.html

 

Gary




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